Java 8 recommendation [GEOS-9619]

[jodygarnett]

Taking discussion from #4243 into a pull request with concrete changes.

Checklist

For all pull requests:

• Confirm you have read the contribution guidelines
• You have sent a Contribution Licence Agreement (CLA) as necessary (not required for small changes, e.g., fixing typos in documentation)
• Make sure the first PR targets the master branch, eventual backports will be managed later. This can be ignored if the PR is fixing an issue that only happens in a specific branch, but not in newer ones.

The following are required only for core and extension modules (they are welcomed, but not required, for community modules):

• There is a ticket in Jira describing the issue/improvement/feature (a notable exemptions is, changes not visible to end users)
• PR for bug fixes and small new features are presented as a single commit
• Commit message must be in the form "[GEOS-XYZW] Title of the Jira ticket" (export to XML in Jira generates the message in this exact form)
• The pull request contains changes related to a single objective. If multiple focuses cannot be avoided, each one is in its own commit and has a separate ticket describing it.
• New unit tests have been added covering the changes
• This PR passes all existing unit tests (test results will be reported by travis-ci after opening this PR)
• This PR passes the QA checks (QA checks results will be reported by travis-ci after opening this PR)
• Commits changing the UI, existing user workflows, or adding new functionality, need to include documentation updates (screenshots, text)
• Commits changing the REST API, or any configuration object, should check if the REST API docs (Swagger YAML files and classic documentation) need to be updated.

[jodygarnett]

Used this into on the prior page where it talks about java versions.

[jodygarnett]

While I do not think anyone is working on Java 5 anymore this is much easier to read as a table

[jodygarnett]

Clear recommendation of Java 8, provides a summary of the options, and then a heading to explore each idea.

[jodygarnett]

New heading for Java 11, provides a summary of options, this way it is very clear Java 11 works out of the box and does not have as many optional installs.

[jodygarnett]

Clear Java 8 subheading for Native JAI and ImageIO, and clearly not recommended.

I considered taking this section to the wiki and removing it from our day-to-day user manual.

[aaime]

Looks good to me, just suggested a minor wording change.